Solid state image sensors (“imagers”) comprise a two-dimensional array of imaging pixels in combination with control and readout circuitry. The imaging pixels detect incident radiation and produce output signals. The control and readout circuitry reads the output signals and processes them to produce an image.
FIG. 1 illustrates the layout of an imaging array 100 of an imager having nine imaging pixels 102a-102i arranged in three rows (i−1; i+1) and three columns (j−1; j; j+1). Each of the imaging pixels 102a-102i includes a photodetector 104, which produces an output signal in response to receiving incident radiation. As mentioned, the output signals are read out and processed by control and readout circuitry (not shown) to produce an image.
The performance of an imager may be characterized by various metrics, one of which is the dynamic range. The dynamic range of an imager is a measure of the maximum optical signal (where the optical signal refers to light intensity) the imaging pixels can detect during an integration period before saturating (referred to herein as the “light saturation level”) compared to the minimum optical signal the imaging pixels can detect, and thus represents the ability of an imager to accurately portray both bright and dark areas in an image. An imager with a relatively high dynamic range saturates at a relatively large optical signal compared to the minimum optical signal it can detect, and therefore may be able to produce images that more accurately portray scenes with high contrast (i.e., bright and dark areas) than an imager with a relatively lower dynamic range.